Process for crimping abrasive fibers



Sept. 3, 1968 R. c. KNOWLTON PROCESS FOR CRIMPING ABRASIVE FIBERS FiledJan. 24, 1967 FIG.

FIG.

FIG.

FIG.

INVENTOR ROBERT C. KN OWLTON ATTORNEY United States Patent 3,399,439PROCESS FOR CRIMPING ABRASIVE FIBERS Robert C. Knowlton, Kinston, N.C.,assignor to E. I. du Pont de Nemours and Company, Wilmington, Del., acorporation of Delaware Filed Jan. 24, 1967, Ser. No. 611,385 4 Claims.(CI. 28-72) ABSTRACT OF THE DISCLOSURE The improvement in the process ofcrimping synthetic filamentary tows which are abrasive to metals whilein high pressure rubbing contact therewith in a stutter-box typecrimper. The improvement comprising blending from 5% to 55% of anon-abrasive fiber with the abrasive fiber prior to crimping and guidingthe blend components through the stutter-box crimper in such a manner aswill provide a shield of the relatively non-abrasive fiber between theabrasive fiber and the stationary portions of the crimping apparatusthat contact the moving tow thereby reducing wear and the attendantfiber damage.

BACKGROUND OF THE INVENTION Field of the invention This inventionrelates to stutter-box crimping of synthetic filamentary tows and moreparticularly to an improved process for crimping of tows which areabrasive under high-pressure rubbing contact with metals.

Description of the prior art It is well-known to crimp syntheticfilamentary tows in apparatus comprising a set of advancing rolls whichforce the tow into a channel the egress from which is blocked by a gateurged toward the closed position by one of a variety of means. Suchcrimping apparatus is described in the Hitt U.S. Patent 2,747,233 whichissued May 29, 1956, for example. In these crimpers, the advancing rollsare yieldably loaded toward each other to permit the slight opening andclosing motion required to accommodate the inavoidable slight variationsin thickness of the tow in their nip due to position-to-positionmigration of individual filaments over preceding guides. The filamentsare prevented from spreading beyond the ends of the rolls by thepresence of disc shaped inserts which are held firmly against the rollsat each end of the nip.

It has been found that certain types of filamentary tows may notcontinuously be processed to crimped tows of good quality in stutter-boxcrimpers known to the art. Products which tend to abrade metals underrubbing, high-pressure contact will rapidly wear the discs to form adepression with sharp edges therein. The tow is severely damaged bycontact with such worn discs thereby necessitating frequent processinterruptions for disc replacement to avoid an unacceptable level offilament breaks at the edges of the tow.

Products which tend to abrade metals include those fibers classified asdull in luster due to the presence of a rather large amount ofdelustering (opacifying) pigment such as titania and also those fiberswhich have an intentionally roughened surface resulting from theincorporation of other particulate matter that may be larger in size andsmaller in quantity than the titania delustrant. The dull productsprovide improved cover (opacity) in fabrics constructed from them andthe roughened fiber finds a variety of uses where a lower fiber-to-fiberfriction is desirable.

Rosenstein et al. U.S. Patent 3,164,882, which issued Jan. 12, 1965,teaches the use of an endless cushion apron 3,399,439 Patented Sept. 3,1968 ice or limp flexible sheathing which is made of a filament sliver,knitted or woven webbing or such like mateiial of a durable and pliablenature for protecting the filaments being crimped as they pass betweenthe pressing means within the stutter-box type crimper. Rosenstein etal. among other things, is concerned with crimping fibers whichheretofore could not be crimped because of their inability to withstandstresses or strains exerted transversely of their longitudinal axis. Thepresent invention concerns the improvement in the process of crimpingfibers that are abrasive to metals and the reduction of the attendantfiber damage from rubbing the otherwise abraded metal parts of thecrimper. The present invention also accomplishes its purpose withoutreduction in crimper capacity. In the present invention the shieldingfiber (lowabrasive) is part of the production being crimped whereas inRosenstein the endless sheathings are in essence being crimped but arenot part of the crimper production, thereby decreasing the crimperefiiciency.

Rosenstein teaches nothing about the abrasiveness of the sheathing ascompared to the abrasiveness of the production being crimped.

Though the process of Rosenstein et al. may lessen fiber damage causedby high pressure rubbing contact of the fiber against the stationarymetal parts of the crimper it does not accomplish this goal in a manneranalogous to that of the present invention. Rosenstein lessens thedamage by advancing the cushion sheathing simultaneously with theproduction filaments being crimped, thereby preventing high pressurerubbing contact between the faces of the production rope and thecrimper. The present invention accomplishes its purpose withouteliminating high pressure rubbing contact between production and thecrimper as in Rosenstein et al. at the expense of crimper efficiency,but accomplishes its purpose by the critical seletcion of shield fibersdesigned to be compatible with the highly abrasive fiber in textilefabrics prepared from them and to be relatively low in abrasion of metalwhile in high pressure rubbing contact therewith.

A process for stutter-box crimping of abrasive fibers without theattendant fiber damage is highly desirable.

SUMMARY This invention provides an improved process for crimping fibersthat are abrasive to metals.

This and other advantages are provided by this improvement invention inthe process for crimping fibers which are abrasive to metals whichcomprises blending from 5% to 55%, preferably 10% to 25% of a lowabrasive fiber with the abrasive fibers prior to crimping and guidingthe blend components to the stuffing-rolls nip in such a manner as willprovide a shield of relatively non-abrasive fiber between the abrasivefiber and the crimper discs which are inserted adjacent the nip of thestulfing rolls to hold the tow within the nip and to guide the tow intothe crimper. The non-abrasive filaments may be any of the class offibers which are relatively low in disc-wear rate, but it generally willbe preferable to choose as the shield fiber one which otherwiseresembles the predominant fiber in physical and chemical properties asclosely as possible. In this manner, the presence of the shield as adiluent will have little or no effect on the characteristics of theproducts made therefrom. It will be recognized, however, that to attaincertain novel or spe cial effects it may be desirable to employ as ashield fiber one which has distinctly different characteristics.

Subsequent to crimping, the tow may be handled in a variety of waysdepending on its intended utility. If cut to staple, the two types offiber will be intimately blended by subsequent processing to usefulstructures. It finished as tow for textile processing on one of thetow-breaking means, blending of the two fiber components will beaccomplished in the early stages of the series of subsequent operationsassociated with this system.

BRIEF DESCRIPTION OF THE DRAWING FIGURE 1 is a diagrammatic sketch of astuifer box type crimper that is useful in carrying out the process ofthis invention. The tow to be crimped is indicated by 5 and the drivenfeed rolls are indicated by numerals 6 and 7.

FIGURE 2 is a view taken on line 2-2 of FIGURE 1 to illustrate theimprovement feature in the crimping process of this invention which isthe reduction of the frictional wear of the inserts 8 and 9 andreduction of the resulting fiber and tow damage caused by high pressurerubbing contact of the edges of the tow 5 with the inserts.

FIGURE 3 is a view of the tow prior to crimping taken across the towwidth with the semidull (low abrasive) edges indicated by 10 FIGURE 4 isa view taken across the tow width after crimping with the semidull (lowabrasive) edges indicated by 10.

A more complete description of the stufiing box type crimper useful incarrying out the process of this invention may be had by reference toHitt, US. Patent 2,311,- 174, which issued Feb. 16, 1943, and to Hitt,U.S. Patent 2,747,233, which issued May 29, 1956.

This invention is further illustrated by the following example.

EXAMPLE A total of 46 bobbins of 600-filament, 1.5 denier-perfilamentdrawn polyester yarn is crimped in a stufiingbox crimper. Forty-two ofthe bobbins are dull in luster due to presence of 2.0% Ti0 delustrant;four bobbins contain semidull yarn which has 0.3% TiO Two of thesemidull yarn ends are guided in such a manner as to lie predominantlyat the back side of the bundle as it is guided to the crimper therebyserving as a shield between the dull tow and the back side of thecrimper. The remaining two semidull ends are blended with the 42 dullyarns nearer the front side of the bundle. The following tablesummarizes the results obtained, including a comparison test involvingonly semidull yarn.

It will be seen that the presence of semidull fiber adjacent to thecrimper disc during crimping of dull fiber substantially reduces therate of wear, but that the advantages of this invention are bestobtained by guiding the shield fiber so as to lie between the abrasivefiber and the discs.

In a second test, in which 24% semidull fiber was equally divided andoriented at both sides of a dull tow, abrasion depth was found toaverage -75 microns after 40 minutes of operation, compared with 150microns during processing of dull tow.

What is claimed is:

1. In the process of crimping a plurality of continuous filament yarnswhich are highly abrasive to metal while in high pressure rubbingcontact therewith and having opacifying particulate matter in the yarns,the process being of the type including the steps of (a) continuouslybringing together in the form of a rope a plurality of separated yarns;

(b) continuously guiding said rope of yarns into the nip of a. pair ofcounter-rotating rotary pressure members;

(c) discharging said yarns from said nip into an enclosed housingadapted to accumulate and restrain the yarns, whereby the individualcontinuous filaments of said yarns are caused to continuously crimp asthey are discharged from said nip, the yarns being held within said nipand guided to said housing by means of inserts held firmly against theends of said P;

(d) releasing the resultant crimped yarns from said housing;

wherein the improvement comprises (e) continuously guiding on the edgesof said rope in step (a) from 5% to 55% based on total rope of lowabrasive yarns having a lesser amount of opacifying particulate matter;

(f) guiding said low abrasive yarn in step (b) between said highabrasive yarn and said inserts whereby said low abrasive yarn shieldsthe high abrasive yarn from high pressure rubbing contact with saidinserts; and then (g) combining said low abrasive yarn with said highabrasive yarn;

said low abrasive yarn being compatible in textile fabrics with saidhigh abrasive yarn.

2. The process as in claim 1 wherein said low abrasive yarn in step (e)is from 10% to 25% of the total rope.

3. The process as in claim 1 wherein said high abrasive yarns containfrom 1% to about 3% titania pigment (TiO and said low abrasive yarnscontain from about 0.1% to about 0.5% of titania pigment (TiO 4. Theprocess as in claim 3 wherein said high and low abrasive yarns areessentially polyesters.

References Cited UNITED STATES PATENTS 1,893,809 1/1933 Stone et al.

FOREIGN PATENTS 962,516 7/1964 Great Britain.

LOUIS K. RIMRODT, Primary Examiner.

